Nixon M R, Orr A G, Vukusic P
School of Physics, University of Exeter, Exeter EX4 4QL, UK
School of the Environment, Griffith University, Nathan, Queensland 4111, Australia.
J R Soc Interface. 2015 Feb 6;12(103). doi: 10.1098/rsif.2014.0749.
The dorsal surfaces of the hindwings of the dragonfly Rhyothemis resplendens (Odonata: Libellulidae) reflect a deep blue from the multilayer structure in its wing membrane. The layers within this structure are not flat, but distinctly 'wrinkled', with a thickness of several hundred nanometres and interwrinkle crest distances of 5 µm and greater. A comparison between the backscattered light from R. resplendens and a similar, but un-'wrinkled' multilayer in the damselfly Matronoides cyaneipennis (Odonata: Calopterygidae) shows that the angle over which incident light is backscattered is increased by the wrinkling in the R. resplendens structure. Whereas the reflection from the flat multilayer of M. cyaneipennis is effectively specular, the reflection from the wrinkled R. resplendens multilayer spans 1.47 steradians (equivalent to ±40° for all azimuthal angles). This property enhances the visibility of the static wing over a broader angle range than is normally associated with a smooth multilayer, thereby markedly increasing its conspicuousness.
丽色丝蟌（蜻蜓目：蜻科）后翅的背面因其翅膜中的多层结构而反射出深蓝色。该结构中的各层并非平整的，而是明显“起皱”，厚度达数百纳米，相邻褶皱嵴之间的距离为5微米或更大。对丽色丝蟌的背散射光与豆娘蓝翅蟌（蜻蜓目：色蟌科）中类似但未“起皱”的多层结构进行比较表明，丽色丝蟌结构中的褶皱增加了入射光背散射的角度范围。蓝翅蟌平整多层结构的反射实际上是镜面反射，而丽色丝蟌起皱多层结构的反射范围为1.47球面度（相当于所有方位角的±40°）。这一特性使静止翅膀在比光滑多层结构通常所具有的更宽角度范围内更易被看到，从而显著增加了其醒目程度。
